14. GIGASPERMACEAE Lindberg

Ann E. Rushing

Plants minute, with upright branches arising from pale, fleshy, subterranean, aphyllous stems. Leaves crowded distally, broadly concave, ovate, elliptic to obovate costa single or absent; cell walls of lamina often thickened at corners. Sexual condition paroicous [synoicous, or occasionally dioicous]. Seta short to moderately elongate. Capsule globose or hemispheric, commonly spongy or wrinkled, immersed or exserted, gymnostomous or cleistocarpous. Calyptra very small, conic [mitrate], fugacious. Genera 6, species 9 (1 in the flora): s United States, usually Southern Hemisphere. The major defining feature of Gigaspermaceae is the fleshy, underground stem from which short gametophore branches are produced in abundance. Sporophyte features differentiate the six, mostly monotypic genera, Chamaebryum Thériot & Dixon in South Africa, Thériot in South America, Gigaspermum Lindberg in Mexico, South Africa, Australia, and Pacific Islands (New Zealand), Lorentziella in southern United States and South America, Neosharpiella H. Robinson & Delgadillo in Mexico and South America, and Oedipodiella Dixon in South Africa.

SELECTED REFERENCE Fife, A. J. 1980. The affinities of Costesia and Neosharpiella and notes on the Gigaspermaceae (Musci). Bryologist 83: 466–476.

1. LORENTZIELLA Müller Hal., Linnaea 42: 229. 1879 · [For Paul Günter Lorentz, 1835–1881, German bryologist]

Leaves imbricate distally, concave, broadly ovate to elliptic, abruptly narrowed to a long awn; costa narrow, extending to base of awn. Capsule immersed to slightly emergent, base truncate, operculum not differentiated. Species 1 or 2 (1 in the flora): United States, s South America. Lorentziella is a genus of minute, ephemeral comprising one, or at most two, species. The perennial, subterranean stem or rhizome system gives rise to upright, above-ground in late fall–early winter. Above-ground plants are produced in abundance during mild, wet winters but less commonly when conditions are dry. The broadly concave leaves completely surround the globose, cleistocarpous capsules of immersed sporophytes. The glaucous, blue-

202 Lorentziella · GIGASPERMACEAE 203 green color of the above-ground plants is reminiscent of Bryum argenteum while their cabbage shape resembles a small Funaria gametophyte prior to elongation of seta.

SELECTED REFERENCES Lawton, E. 1953. Lorentziella, a genus new to North America. Bull. Torrey Bot. Club 80: 279– 288. Rushing, A. E. and J. A. Snider. 1980. Observations on sporophyte development in Lorentziella imbricata (Mitt.) Broth. J. Hattori Bot. Lab. 47: 35–44.

1. Lorentziella imbricata (Mitten) Brotherus in H. G. A. truncate base, 1–1.5 mm long, 1–2 mm in diameter; Engler and K. Prantl, Nat. Pflanzenfam. 216[I,3]: 511. stomata at base of capsule with a central opening in an 1903 imperfectly divided single, 2-nucleate guard cell. Calyptra Leptangium imbricatum Mitten, narrowly conic, covering tip of capsule. Spores of 2 sizes: J. Linn. Soc., Bot. 12: 240. 1869; large, faintly granulose, yellow-brown, 120–160 µm, and Acaulon runyonii Grout; small, densely granular, shriveled, 32–73 µm. A. megalosporum Grout Capsules mature winter. Often found in loose soil at granitic outcrop margins in association with Selaginella; Plants small, bulbiform in shape low to moderate elevations; Tex.; South America with distally densely crowded (Argentina, Paraguay, Uruguay). 5 leaves, light green to glaucous, in Lorentziella imbricata is known from Bastrop, Brazos, dense clusters or tufts. Stems Burnet, Cameron, Gillespie, Llano, and Travis counties above ground erect, 2–5 mm. in central Texas. It is named for the closely imbricate Leaves 1.5–4 mm; proximal leaves less crowded, ovate distal leaves. In Texas, fertilization and sporophyte with acute tips; margins entire to weakly serrate; distal growth occur in the winter months and by late spring laminal cells elongate, oblong-hexagonal to short- little trace of the above-ground plants remain. Spores rhomboidal; proximal laminal cells quadrate to short- have been described as angular, probably due to packing rectangular. Sexual condition paroecious with antheridia and space constraints within the capsule. Stomata have in naked clusters in axils of distal leaves. Seta short, less been described as having a single guard cell with a central than 0.25 mm. Capsule immersed to slightly emergent opening or two guard cells. Careful study of guard cells when mature and fully expanded, pale green, reveals that most are single-celled, 2-nucleate with a cleistocarpous, globose to ellipsoidal or ovate with a central opening.